1. Field of Invention
The present invention relates to a system including a bi-directional drive mechanism, which permits a power transmission from a driving side to a driven side in a bi-direction but prevents a power transmission from the driven side to the driving side.
More particularly, the present invention relates to a door lock system for an automotive vehicle, which includes a clutch so that when a door lock is manually operated, door lock is by means of the clutch operatively disconnected from a driving device having an electric motor, whereby the door lock can be operated with a small force.
2. Brief Description of Prior Art
In a conventional door lock system, it is known that a clutch mechanism is employed in a door lock driving device so that a door lock can be manually operated with a small force.
For example, in a conventional system of this kind disclosed in Japanese Patent Publication No. 58-30473, a swing lever is rotatably supported by a driving shaft carrying a driving gear thereon, an operation gear is rotatably supported by the swing lever and engaged with the driving gear, and a spring washer is interposed between the swing lever and the operation gear for applying a frictional force when the operation gear rotates around its own axis. In this prior art, there are further provided an internal gear which is brought into engagement with the operation gear when the operation gear rotates around the driving shaft and an expansion coil connected to the swing lever for driving the operation gear to a neutral position where the operation gear and the internal gear are out of engagement with each other.
The above explained prior art door lock device has, however, the following disadvantage. Since the swing lever is held at its neutral position by the spring force of the expansion spring, the frictional force applied to the operation gear by the spring washer should be large enough to overcome the spring force of the expansion spring so as to rotate the swing lever around the driving shaft and to bring the operation gear into engagement with the internal gear. Accordingly, a large amount of torque loss appears at the operation gear and a larger rotational force is required to drive the operation gear, which makes inevitably an electric motor larger in its size and a larger amount of power consumption can not be avoided.